The present application relates generally to an improved data processing apparatus and method and more specifically to mechanisms for extending cache for an external storage system into individual servers.
A storage area network (SAN) is a dedicated storage network that provides access to consolidated, block level storage. SANs primarily make storage devices accessible to servers so that the devices appear as locally attached to the operating system. A SAN may have its own network of storage devices that are generally not accessible through the regular network by regular devices.
In a typical configuration, external storage systems connect by a SAN. Inside the storage system is a cache, which typically comprises dynamic random access memory (DRAM). The cache reduces latency seen by the server; however, this cache stores most recently used data by all servers attached to the external storage system. SAN delays and delay in the storage system due to cache misses affect latency.